U.S. patent application number 15/545785 was filed with the patent office on 2018-01-18 for control device for vehicle and control method for vehicle.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. The applicant listed for this patent is NISSAN MOTOR CO., LTD.. Invention is credited to Ken ITO, Yuji KATSUMATA, Hiroyuki KOMATSU, Takashi NAKAJIMA, Akira SAWADA.
Application Number | 20180015925 15/545785 |
Document ID | / |
Family ID | 56542638 |
Filed Date | 2018-01-18 |
United States Patent
Application |
20180015925 |
Kind Code |
A1 |
KOMATSU; Hiroyuki ; et
al. |
January 18, 2018 |
CONTROL DEVICE FOR VEHICLE AND CONTROL METHOD FOR VEHICLE
Abstract
The device that generates the friction braking force to
decelerate the vehicle estimates the disturbance torque acting on
the vehicle. When the accelerator operation amount is equal to or
less than the predetermined value and the vehicle is just before
the stop of the vehicle, the control device for vehicle causes the
friction braking amount to converge to the friction braking amount
to the value decided on the basis of the disturbance torque
estimated value Td in conjunction with the reduction in the motor
rotation speed (speed parameter) proportionate to the traveling
speed of the vehicle.
Inventors: |
KOMATSU; Hiroyuki;
(Kanagawa, JP) ; ITO; Ken; (Kanagawa, JP) ;
NAKAJIMA; Takashi; (Kanagawa, JP) ; KATSUMATA;
Yuji; (Kanagawa, JP) ; SAWADA; Akira;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NISSAN MOTOR CO., LTD. |
Yokohama-shi, Kanagawa |
|
JP |
|
|
Assignee: |
NISSAN MOTOR CO., LTD.
Yokohama-shi, Kanagawa
JP
|
Family ID: |
56542638 |
Appl. No.: |
15/545785 |
Filed: |
January 26, 2015 |
PCT Filed: |
January 26, 2015 |
PCT NO: |
PCT/JP2015/052083 |
371 Date: |
July 24, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 2552/15 20200201;
B60T 8/17 20130101; B60W 40/105 20130101; B60L 7/24 20130101; B60T
2270/604 20130101; B60L 7/10 20130101; B60T 7/12 20130101; B60W
2710/18 20130101; B60L 2260/22 20130101; B60W 2720/106 20130101;
B60W 2520/10 20130101; B60Y 2300/89 20130101; B60L 2240/16
20130101; B60W 10/08 20130101; Y02T 10/72 20130101; B60T 8/58
20130101; B60W 30/181 20130101; B60W 2510/083 20130101; B60T 13/586
20130101; B60W 2540/10 20130101; B60W 30/18127 20130101; B60L 15/20
20130101; B60T 13/588 20130101; B60T 2270/82 20130101; B60W
2710/182 20130101; B60T 2230/04 20130101; B60W 10/184 20130101;
B60W 2510/081 20130101; B60T 1/10 20130101; F16D 61/00 20130101;
B60T 8/17555 20130101 |
International
Class: |
B60W 30/18 20120101
B60W030/18; B60L 7/10 20060101 B60L007/10; B60W 40/105 20120101
B60W040/105; B60W 10/08 20060101 B60W010/08; B60W 10/184 20120101
B60W010/184 |
Claims
1.-10. (canceled)
11. A control device for vehicle that generates a friction braking
force to decelerate a vehicle, the control device for vehicle
comprising: a speed parameter detecting unit configured to detect a
speed parameter proportionate to a traveling speed of the vehicle;
an accelerator operation amount detecting unit configured to detect
an accelerator operation amount; a disturbance torque estimating
unit configured to estimate a disturbance torque acting on the
vehicle; a friction-braking-amount adjusting unit configured to
electrically adjust a friction braking amount; and a control unit
configured to cause the friction braking amount to converge to a
value decided on the basis of the disturbance torque in conjunction
with a reduction in the speed parameter when the accelerator
operation amount is equal to or less than a predetermined value and
the vehicle is just before a stop of the vehicle.
12. The control device for vehicle according to claim 11, further
comprising a speed feedback torque calculating unit configured to
multiply the speed parameter by a predetermined gain to calculate a
speed feedback torque, wherein the control unit decides the
friction braking amount on the basis of the speed feedback torque
and the disturbance torque.
13. The control device for vehicle according to claim 11, wherein
the disturbance torque estimating unit estimates the disturbance
torque on the basis of a model for a transfer characteristic of the
speed parameter with respect to a torque input to the vehicle and
the friction braking amount.
14. The control device for vehicle according to claim 13, further
comprising a detecting unit configured to detect a
friction-braking-amount-related value related to the friction
braking amount, wherein the friction braking amount is used by the
disturbance torque estimating unit to estimate the disturbance
torque, the friction braking amount being calculated on the basis
of the friction-braking-amount-related value detected by the
detecting unit.
15. The control device for vehicle according to claim 13, wherein
the friction braking amount used by the disturbance torque
estimating unit to estimate the disturbance torque is a
friction-braking-amount command value.
16. The control device for vehicle according to claim 13, wherein
the disturbance torque estimating unit estimates the disturbance
torque on the basis of a model for a transfer characteristic of the
speed parameter with respect to the torque input to the vehicle, a
model for a transfer characteristic of the speed parameter with
respect to an input of the friction braking amount to the vehicle,
and the friction braking amount.
17. The control device for vehicle according to claim 11, further
comprising: a first torque target value calculating unit configured
to calculate a first torque target value on the basis of vehicle
information; a second torque target value calculating unit
configured to calculate a second torque target value, the second
torque target value converging to the disturbance torque in
conjunction with the reduction in the speed parameter; and a
just-before-stop determining unit configured to compare a magnitude
of the first torque target value with a magnitude of the second
torque target value to determine whether the vehicle is just before
the stop of the vehicle, wherein the control unit decides the
friction braking amount on the basis of the first torque target
value when the vehicle is determined as not being just before the
stop of the vehicle, and the control unit decides the friction
braking amount on the basis of the second torque target value when
the vehicle is determined as being just before the stop of the
vehicle.
18. The control device for vehicle according to claim 11, wherein
the speed parameter is a rotation speed of a power engine,
19. The control device for vehicle according to claim 18, further
comprising a power engine torque adjusting unit configured to cause
a torque from the power engine to converge to the disturbance
torque in conjunction with a reduction in the rotation speed of the
power engine when the accelerator operation amount is equal to or
less than a predetermined value and the vehicle is just before the
stop of the vehicle on an uphill road.
20. A control method for vehicle that generates a friction braking
force to decelerate a vehicle, the control method for vehicle
comprising: detecting a speed parameter proportionate to a
traveling speed of the vehicle; detecting an accelerator operation
amount; estimating a disturbance torque acting on the vehicle; and
causing a friction braking amount to converge to the disturbance
torque in conjunction with a reduction in the speed parameter when
the accelerator operation amount is equal to or less than a
predetermined value and the vehicle is just before a stop of the
vehicle.
Description
TECHNICAL FIELD
[0001] The present invention relates to a control device for
vehicle and a control method for vehicle.
BACKGROUND ART
[0002] Conventionally, a regenerative brake control device for
electric vehicles provided with setting means capable of any given
setting of a regenerative braking force of a motor and regenerates
the motor by the regenerative braking force set by the setting
means is known (see JP8-79907A).
SUMMARY OF INVENTION
[0003] However, if the regenerative braking force set by the
setting means is large, the following problem occurs. A vibration
in a longitudinal direction of a vehicle body may be generated when
the electric vehicle is decelerated by the set regenerative braking
force and the speed becomes 0.
[0004] An object of the present invention is to provide a technique
that reduces the generation of vibration in a longitudinal
direction of a vehicle body in stopping a vehicle.
[0005] A control device for vehicle according to an embodiment is
that a control device for vehicle of the one embodiment is the
device that generates the friction braking force to decelerate the
vehicle. The control device for vehicle is includes a speed
parameter detecting means configured to detect a speed parameter
proportionate to a traveling speed of the vehicle, an accelerator
operation amount detecting means configured to detect an
accelerator operation amount, a disturbance torque estimating means
configured to estimate a disturbance torque acting on the vehicle,
and a friction-braking-amount adjusting means configured to
electrically adjust a friction braking amount. Further, the control
device for vehicle includes a control means configured such that
the control means causes the friction braking amount to converge to
a value decided on the basis of the disturbance torque in
conjunction with a reduction in the speed parameter when the
accelerator operation amount is equal to or less than a
predetermined value and the vehicle is just before a stop of the
vehicle.
[0006] Embodiments of the present invention and merits of the
present invention will be described below in detail together with
the attached drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a block diagram illustrating a main configuration
of an electric vehicle with a control device for vehicle according
to one embodiment.
[0008] FIG. 2 is a flowchart showing a flow of processes for a
motor current control performed by a motor controller.
[0009] FIG. 3 is a diagram illustrating an example of an
accelerator position (accelerator opening degree)-torque table.
[0010] FIG. 4 is a diagram modeling a drive force transmission
system of the vehicle.
[0011] FIG. 5 is a block diagram for achieving a stop control
process.
[0012] FIG. 6 is a diagram describing a method for calculating a
motor rotation speed F/B torque T.omega. on the basis of a motor
rotation speed .omega.m.
[0013] FIG. 7 is a block diagram describing a method for
calculating a disturbance torque estimated value Td on the basis of
the motor rotation speed .omega.m, a motor torque command value
Tm*, and a friction-braking-amount command value Tb*.
[0014] FIG. 8A are diagrams illustrating control results in the
case where the control device for vehicle of the one embodiment
performs a stop control process on an uphill road.
[0015] FIG. 8B are diagrams illustrating control results in the
case where the control device for vehicle of the one embodiment
performs the stop control process on a flat road.
[0016] FIG. 8C are diagrams illustrating control results in the
case where the control device for vehicle of the one embodiment
performs the stop control process on a downhill road.
DESCRIPTION OF EMBODIMENTS
[0017] The following describes an example that applies a control
device for vehicle according to the present invention to an
electric vehicle.
[0018] FIG. 1 is a block diagram illustrating a main configuration
of the electric vehicle with a control device for vehicle according
to one embodiment. Particularly, the control device for vehicle
according to the embodiment can be applied to a vehicle capable of
controlling acceleration/deceleration and a stop of the vehicle
only by an operation of an accelerator pedal. In this vehicle, a
driver depresses the accelerator pedal during acceleration and
reduces or zeros a depression amount of the depressed accelerator
pedal during deceleration or during stop. It should be noted that,
the vehicle approaches the stop state while the driver depresses
the accelerator pedal to prevent the vehicle from retreating on
uphill roads in some cases. When the vehicle approaches the stop
state by the accelerator pedal operation by the driver, a brake
controller, which will be described later, actuates a friction
brake to decelerate or stop the vehicle. That is, the control
device for vehicle of the embodiment can electrically adjust a
braking amount of the friction brake regardless of the brake pedal
operation by the driver.
[0019] A motor controller 2 has signals indicating vehicle states
such as a vehicle speed V, an accelerator position AP, a rotator
phase .alpha. of a motor (three-phase alternating current motor) 4
and currents iu, iv, and iw of the motor 4, which are input to the
motor controller 2 in the form of digital signals, and generates
PWM signals for controlling the motor 4 on the basis of the input
signals. The motor controller 2 generates a drive signal of an
inverter 3 by the generated PWM signal. The motor controller 2
further generates a friction-braking-amount command value by a
method described later.
[0020] The inverter 3 includes, for example, two switching elements
(e.g. power semiconductor elements such as IGBTs or MOS-FETs) for
each phase, converts a direct current supplied from a battery 1
into an alternating current by turning on and off the switching
elements in accordance with the drive signal and causes a desired
current to flow into the motor 4.
[0021] The motor 4 generates a drive force by the alternating
current supplied from the inverter 3 and transmits the drive force
to right and left drive wheels 9a and 9b via a speed reducer 5 and
a drive shaft 8. Further, when being rotated following the rotation
of the drive wheels 9a and 9b during the travel of the vehicle, the
motor 4 generates a regenerative drive force, thereby collecting
the kinetic energy of the vehicle as electrical energy. In this
case, the inverter 3 converts an alternating current generated
during the regenerative operation of the motor 4 into a direct
current and supplies the direct current to the battery 1.
[0022] A current sensor 7 detects the three-phase alternating
currents iu, iv and iw flowing in the motor 4. Note that, since the
sum of the three-phase alternating currents iu, iv and iw is 0, the
currents of any of two phases may be detected and the current of
the remaining one phase may be obtained by calculation.
[0023] A rotation sensor 6 is, for example, a resolver or an
encoder and detects the rotator phase .alpha. of the motor 4.
[0024] A fluid pressure sensor 10 detects a brake fluid
pressure.
[0025] A brake controller 11 generates the brake fluid pressure
according to the friction-braking-amount command value, which is
generated by the motor controller 2. The brake controller 11
performs a feedback control such that the brake fluid pressure
detected by the fluid pressure sensor 10 follows a value decided
according to the friction-braking-amount command value.
[0026] Friction brakes 12 are disposed at the right and left drive
wheels 9a and 9b. The friction brake 12 presses a brake pad to a
brake rotor according to the brake fluid pressure to generate a
braking force to the vehicle.
[0027] FIG. 2 is a flowchart showing a flow of processes for a
motor current control performed by the motor controller 2.
[0028] In Step S201, signals indicating the vehicle states are
input. Here, the vehicle speed V (km/h), the accelerator position
AP (%), the rotator phase .alpha. (rad) of the motor 4, a rotation
speed Nm (rpm) of the motor 4, the three-phase alternating currents
iu, iv and iw flowing in the motor 4, a direct-current voltage
value Vdc (V) between the battery 1 and the inverter 3, and the
brake fluid pressure are input.
[0029] The vehicle speed V (km/h) is obtained by a vehicle speed
sensor or through communications from another controller (not
illustrated). Alternatively, a vehicle speed v (m/ s) is obtained
by multiplying a rotator mechanical angular velocity .omega.m by a
tire dynamic radius R and dividing the product by a gear ratio of a
final gear, and then the obtained value is multiplied by 3600/1000
for unit conversion, thereby obtaining the vehicle speed V
(km/h).
[0030] The accelerator position AP (%) is obtained from an
accelerator position sensor (not illustrated) or through
communications from another controller such as a vehicle controller
(not illustrated).
[0031] The rotator phase .alpha. (rad) of the motor 4 is obtained
from the rotation sensor 6. The rotation speed Nm (rpm) of the
motor 4 is obtained by dividing a rotator angular velocity .omega.
(electric angle) by a pole pair number p of the motor 4 to obtain a
motor rotation speed .omega.m (rad/s), which is a mechanical
angular velocity of the motor 4, and multiplying the obtained motor
rotation speed .omega.m by 60/ (2.pi.). The rotator angular
velocity .omega. is obtained by differentiating the rotator phase
.alpha..
[0032] The currents iu, iv and iw (A) flowing in the motor 4 are
obtained from the current sensor 7.
[0033] The direct-current voltage value Vdc (V) is obtained from a
voltage sensor (not illustrated) provided in a direct-current power
supply line between the battery 1 and the inverter 3 or a power
supply voltage value transmitted from a battery controller (not
illustrated).
[0034] The fluid pressure sensor 10 detects the brake fluid
pressure.
[0035] In Step S202, a first torque target value Tm1* is set.
Specifically, the first torque target value Tm1* is set on the
basis of the accelerator position AP input in Step S201 and the
motor rotation speed .omega. m by referring to an accelerator
position-torque table illustrated in FIG. 3. Note that, the
accelerator position-torque table is not limited to the table
illustrated in FIG. 3.
[0036] In Step S203, a stop control process to control so as to
stop the electric motor vehicle is performed. Specifically, whether
the electric motor vehicle is just before the stop of the vehicle
is determined. The first torque target value Tm1* calculated in
Step S202 is set as a third torque target value Tm3* before the
electric motor vehicle is just before the stop of the vehicle, and
a second torque target value Tm2*, which converges to a disturbance
torque estimated value Td described later, with a reduction in the
motor rotation speed is set as the third torque target value Tm3*
after the electric motor vehicle is just before the stop of the
vehicle. Then, on the basis of the third torque target value Tm3*,
the motor torque command value Tm* and the friction-braking-amount
command value Tb* are calculated. The brake controller 11 generates
the brake fluid pressure according to the friction-braking-amount
command value Tb* to actuate the friction brake 12, thus
decelerating or stopping the vehicle. The detail of the stop
control process is described later.
[0037] In Step S204, a d-axis current target value id* and a q-axis
current target value iq* are obtained on the basis of the motor
torque command value Tm* calculated in Step S203, the motor
rotation speed .omega.m, and the direct-current voltage value Vdc.
For example, a table defining a relationship of the d-axis current
target value and the q-axis current target value with the motor
torque command value, the motor rotation speed, and the
direct-current voltage value is prepared in advance and the d-axis
current target value id* and the q-axis current target value iq*
are obtained by referring to this table.
[0038] In Step S205, a current control is performed to match a
d-axis current id and a q-axis current iq with the d-axis current
target value id* and the q-axis current target value iq* obtained
in Step S204, respectively. To this end, the d-axis current id and
the q-axis current iq are first obtained on the basis of the
three-phase alternating current values iu, iv and iw and the
rotator phase .alpha. of the motor 4 input in Step S201.
Subsequently, d-axis and q-axis voltage command values vd and vq
are calculated from deviations between the d-axis and q-axis
current command values id* and iq* and the d-axis and q-axis
currents id and iq. It should be noted that a non-interference
voltage necessary to cancel out an interference voltage between d-q
orthogonal coordinate axes may be added to the calculated d-axis
and q-axis voltage command values vd and vq.
[0039] Subsequently, from the d-axis and q-axis voltage command
values vd and vq and the rotator phase .alpha. of the motor 4, the
three-phase alternating-current voltage command values vu, vv, and
vw are obtained. From the obtained three-phase alternating-current
voltage command values vu, vv, and vw and the direct-current
voltage value Vdc, PWM signals tu (%), tv (%), and tw (%) are
obtained. By opening and closing the switching elements of the
inverter 3 by the PWM signals tu, tv and tw obtained in this way,
the motor 4 can be driven with a desired torque instructed by the
torque command value Tm*.
[0040] Here, before the stop control process performed in Step S203
is described, a transfer characteristic Gp(s) from the motor torque
Tm until the motor rotation speed .omega.m and a transfer
characteristic Gp(s) from a friction braking amount Tb until the
motor rotation speed corn in the control device for vehicle
according to the embodiment are described.
[0041] FIG. 4 is a diagram modeling a drive force transmission
system of the vehicle, and respective parameters in the diagram are
as described below. [0042] J.sub.m: inertia of electric motor
[0043] J.sub.w: inertia of drive wheels [0044] M: weight of vehicle
[0045] K.sub.d: torsional rigidity of drive system [0046] K.sub.t:
coefficient relating to friction between tires and road surface
[0047] N: overall gear ratio [0048] r: load radius of tires [0049]
.omega..sub.m: angular velocity of electric motor [0050] T.sub.m:
torque target value Tm* [0051] Td: torque of drive wheels [0052] F:
force applied to vehicle [0053] V: speed of vehicle [0054]
.omega..sub.w: angular velocity of drive wheels [0055] T.sub.b:
friction braking amount (motor axis conversion torque)
[0056] The following equations of motion can be derived from FIG.
4. Note that, the asterisk (*) attached to the right-upper corner
of a symbol in the following Equations (1) to (3) indicates a time
differential. It is defined: T.sub.b>0 with .omega..sub.w>0,
T.sub.b<0 with .omega..sub.w<0, and T.sub.b=0 with
.omega..sub.w=0.
[Equation 1]
J.sub.m.omega..sub.m*=T.sub.m-T.sub.d/N (1)
[Equation 2]
2J.sub.w.omega..sub.w*=T.sub.d-rF-NT.sub.b (2)
[Equation 3]
MV*=F (3)
[Equation 4]
T.sub.d=K.sub.d.intg.(.omega..sub.m/N-.omega..sub.w)dt (4)
[Equation 5]
FK.sub.t(r.omega..sub.w-V) (5)
[0057] To obtain the transfer characteristic Gp(s) from the torque
target value Tm of the motor 4 until the motor rotation speed
.omega.m and a transfer characteristic Gb(s) from the friction
braking amount Tb until the motor rotation speed .omega.m on the
basis of the equations of motion shown in Equations (1) to (5), the
transfer characteristics Gp(s) and Gb(s) are each expressed by the
following Equations (6) and (7).
[ Equation 6 ] G p ( s ) = b 3 s 3 + b 2 s 2 + b 1 s + b 0 s ( a 4
s 3 + a 3 s 2 + a 2 s + a 1 ) ( 6 ) [ Equation 7 ] G b ( s ) = - b
1 s + b 0 s ( a 4 s 3 + a 3 s 2 + a 2 s + a 1 ) ( 7 )
##EQU00001##
[0058] Here, each parameter in Equations (6) and (7) is expressed
by the following Equation (8).
[Equation 8]
a.sub.4=2J.sub.mJ.sub.wM
a.sub.3=J.sub.m(2J.sub.w+Mr.sup.2)K.sub.t
a.sub.2=(J.sub.m+2J.sub.w/N.sup.2)MK.sub.d
a.sub.1=(J.sub.m+2J.sub.w/N.sup.2+Mr.sup.2/N.sup.2)K.sub.dK.sub.t
b.sub.3=2J.sub.wM
b.sub.2=(2J.sub.w+Mr.sup.2)K.sub.t
b.sub.1=MK.sub.d
b.sub.0=K.sub.dK.sub.t (8)
[0059] Through examinations, the poles and 0 points of a transfer
function shown in Equation (6) can be approximated to a transfer
function of the following Equation (9), and one pole and one 0
points indicate values extremely close to each other. This is
equivalent to that a and 13 of the following Equation (9) indicate
values extremely close to each other.
[ Equation 9 ] G p ( s ) = ( s + .beta. ) ( b 2 ' s 2 + b 1 ' s + b
0 ' ) s ( s + .alpha. ) ( a 3 ' s 2 + a 2 ' s + a 1 ' ) ( 9 )
##EQU00002##
[0060] Accordingly, by performing pole-zero cancellation
(approximation to .alpha.=.beta.) in Equation (9), Gp(s)
constitutes a transfer characteristic of (second order)/(third
order) as shown in the following Equation (10).
[ Equation 10 ] G p ( s ) = ( b 2 ' s 2 + b 1 ' s + b 0 ' ) s ( a 3
' s 2 + a 2 ' s + a 1 ' ) .beta. .alpha. ( 10 ) ##EQU00003##
[0061] Next, the detail of the stop control process performed in
Step S203 of FIG. 2 is described.
[0062] FIG. 5 is a block diagram for achieving the stop control
process. A motor rotation speed F/ B torque setting device 501, a
disturbance torque estimator 502, an adder 503, a torque comparator
504, and a command value calculator 505 perform the stop control
process.
[0063] The motor rotation speed F/B torque setting device 501
calculates a motor rotation speed feedback torque (hereinafter
referred to as a motor rotation speed F/B torque) T.omega. on the
basis of the detected motor rotation speed .omega.m.
[0064] FIG. 6 is a diagram describing a method for calculating the
motor rotation speed F/B torque T.omega. on the basis of the motor
rotation speed .omega.m. The motor rotation speed F/B torque
setting device 501 includes a multiplier 601 and calculates the
motor rotation speed F/B torque T.omega. by multiplying the motor
rotation speed .omega.m by a gain Kvref. However, Kvref is a
negative (minus) value necessary to stop the electric motor vehicle
just before the electric motor vehicle stops, and appropriately
set, for example, from experimental data or similar data. The motor
rotation speed F/B torque T.omega. is set as a torque capable of
obtaining a larger braking force as the motor rotation speed
.omega.m increases.
[0065] It should be noted that, although the motor rotation speed
F/B torque setting device 501 is described to calculate the motor
rotation speed F/B torque T.omega. by multiplying the motor
rotation speed .omega.m by the gain Kvref, the motor rotation speed
F/B torque T.omega. may be calculated using, for example, a
regenerative torque table defining a regenerative torque with
respect to the motor rotation speed cm and an attenuation rate
table storing an attenuation rate of the motor rotation speed
.omega.m in advance.
[0066] The disturbance torque estimator 502 illustrated in FIG. 5
calculates the disturbance torque estimated value Td on the basis
of the detected motor rotation speed .omega.m, the motor torque
command value Tm*, and the friction-braking-amount command value
Tb*. The command value calculator 505, which will be described
later, calculates the motor torque command value Tm* and the
friction-braking-amount command value Tb*.
[0067] FIG. 7 is a block diagram describing a method for
calculating the disturbance torque estimated value Td on the basis
of the motor rotation speed cam, the motor torque command value
Tm*, and the friction-braking-amount command value Tb*. The
disturbance torque estimator 502 includes a control block 701, a
control block 702, a control block 703, a control block 704, a
subtractor 705, and a subtractor 706.
[0068] The control block 701 functions as a filter having a
transfer characteristic H(s)/Gp(s) and inputs the motor rotation
speed .omega.m and performs a filtering process, thus calculating a
first motor torque estimated value. H(s) is a low-pass filter
having such a transfer characteristic that a difference between the
denominator degree and the numerator degree is equal to or more
than a difference between the denominator degree and the numerator
degree of the model Gp(s) (see Equation (10)).
[0069] The control block 702 functions as a low-pass filter having
a transfer characteristic H(s) and inputs the motor torque command
value Tm* and performs the filtering process, thus calculating a
second motor torque estimated value.
[0070] The control block 703 functions as a filter having the
transfer characteristic Gb(s) shown in Equation (7) and inputs the
friction-braking-amount command value Tb* and performs the
filtering process, thus calculating a friction braking rotation
speed estimated value. It should be noted that, instead of the
friction-braking-amount command value Tb*, a friction braking
amount calculated on the basis of the brake fluid pressure detected
by the fluid pressure sensor 10 may be used.
[0071] The control block 704 functions as a filter having a
transfer characteristic H(s)/Gp(s) similar to the control block 701
and inputs the friction braking rotation speed estimated value and
performs the filtering process, thus calculating an
amount-of-friction braking estimated value.
[0072] The subtractor 705 subtracts the amount-of-friction braking
estimated value from the second motor torque estimated value to
calculate a third motor torque estimated value.
[0073] The subtractor 706 subtracts the first motor torque
estimated value from the third motor torque estimated value to
calculate the disturbance torque estimated value Td. This
disturbance torque estimated value Td is a value excluding the
friction braking amount.
[0074] It should be noted that although the disturbance torque
according the embodiment is estimated by a disturbance observer as
illustrated in FIG. 7, it may be estimated using a meter such as a
vehicle longitudinal G sensor.
[0075] Here, while an air resistance, a modeling error caused by a
variation of the vehicle weight due to the number of passengers and
load capacity, a rolling resistance of the tires, a gradient
resistance of the road surface, and a similar resistance are
thought as the disturbances, a disturbance factor dominant just
before the stop of the vehicle is the gradient resistance. While
the disturbance factors differ depending on driving conditions, the
disturbance factors described above can be collectively estimated
since the disturbance torque estimator 502 calculates the
disturbance torque estimated value Td on the basis of the motor
torque command value Tm*, the motor rotation speed .omega.m, the
vehicle model Gp(s), and the friction-braking-amount command value
Tb*. This achieves a smooth vehicle stop from deceleration under
any driving condition.
[0076] Returning to FIG. 5, the explanation will be continued. The
adder 503 adds the motor rotation speed F/B torque T.omega.
calculated by the motor rotation speed F/B torque setting device
501 and the disturbance torque estimated value Td calculated by the
disturbance torque estimator 502 to calculate the second torque
target value Tm2*. When the motor rotation speed .omega.m decreases
and approaches 0, the motor rotation speed F/B torque T.omega. also
approaches 0. Accordingly, the second torque target value Tm2*
converges to the disturbance torque estimated value Td according to
the reduction in the motor rotation speed .omega.m.
[0077] The torque comparator 504 compares the magnitudes of the
first torque target value Tm1* with the second torque target value
Tm2* and sets the larger torque target value as the third torque
target value Tm3*. The second torque target value Tm2* is smaller
than the first torque target value Tm1* during the travel of the
vehicle. When the vehicle decelerates and reaches just before the
stop of the vehicle (the vehicle speed is equal to or less than a
predetermined vehicle speed), the second torque target value Tm2*
becomes larger than the first torque target value Tm1*. Thus, when
the first torque target value Tm1* is larger than the second torque
target value Tm2*, the torque comparator 504 determines that the
vehicle is prior to just before the stop of the vehicle and sets
the third torque target value Tm3* to the first torque target value
Tm1*. Further, when the second torque target value Tm2* becomes
larger than the first torque target value Tm1*, the torque
comparator 504 determines that the vehicle is just before the stop
of the vehicle and switches the third torque target value Tm3* from
the first torque target value Tm1* to the second torque target
value Tm2*.
[0078] The command value calculator 505 calculates the motor torque
command value Tm* and the friction-braking-amount command value Tb*
on the basis of the third torque target value Tm3* output from the
torque comparator 504. Here, under the condition where the motor 4
performs the regenerative operation, it is defined: Tb*=|Tm3*| with
Tm*=0 and .omega..sub.w>0, Tb*=0 with .omega..sub.w=0, and
Tb*=|Tm3*| with .omega..sub.w<0. Under the condition where the
motor 4 performs a power running operation, it is defined: Tm*=Tm3*
and Tb*=0. Under the condition where the motor 4 performs the power
running operation means a situation where the vehicle travels by
the drive force from the motor 4 and a situation where the vehicle
is stopped on the uphill road.
[0079] FIG. 8A to FIG. 8C are diagrams illustrating control results
in the case where the control device for vehicle of the one
embodiment performs the stop control process. FIG. 8A to FIG. 8C
are the control results when the vehicle stops on the respective
uphill road, flat road, and downhill road. The respective drawings
express the motor rotation speed, the motor torque, the
friction-braking-amount command value, and the vehicle longitudinal
acceleration in the order from the above.
[0080] First, the following describes the control result when the
vehicle stops on the uphill road with reference to FIG. 8A. A time
before a time t2 is prior to the vehicle being just before the stop
at which the first torque target value Tm1* is larger than the
second torque target value Tm2*.
[0081] At a time ti at which the vehicle is prior to just before
the stop, the first torque target value Tm1* calculated in Step
S202 in FIG. 2 is set to the third torque target value Tm3*. The
vehicle decelerates according to the friction-braking-amount
command value Tb* decided on the basis of the first torque target
value Tm1* (=third torque target value Tm3*).
[0082] At the time t2, when the second torque target value Tm2* is
larger than the first torque target value Tm1* and it is determined
that the vehicle is just before the stop, the third torque target
value Tm3* switches from the first torque target value Tm1* to the
second torque target value Tm2*. Accordingly, the
friction-braking-amount command value Tb* also switches from the
value decided on the basis of the first torque target value Tm1* to
the value decided on the basis of the second torque target value
Tm2*. At the time t2 or after the time t2, the second torque target
value Tm2* (=third torque target value Tm3*) converges to the
disturbance torque estimated value Td according to the reduction in
the motor rotation speed .omega.m.
[0083] The third torque target value Tm3* converging to the
disturbance torque estimated value Td switches from a negative
value to a positive value between the times t2 and t3. At a point
where the third torque target value Tm3* switches from the negative
value to the positive value, the friction-braking-amount command
value Tb* becomes 0, and a deceleration adjustment by the power
running operation of the motor 4 starts. The motor torque command
value Tm* having 0 until the third torque target value Tm3*
switches from the negative value to the positive value afterward
matches the third torque target value Tm3* and converges to the
disturbance torque estimated value Td.
[0084] At a time t5, the motor torque command value Tm*
(=Tm3*=Tm2*) converges to the disturbance torque estimated value Td
and the motor rotation speed .omega.m asymptotically converges to
0. This achieves the smooth vehicle stop without acceleration
vibration in the longitudinal direction. When the motor torque
command value Tm* matches the disturbance torque estimated value
Td, the vehicle stop state is maintained on the uphill road as well
at the time t5 and after the time t5.
[0085] It should be noted that, the above-described explanation
describes that the friction-braking-amount command value Tb*
becomes 0 at the point where the third torque target value Tm3*
switches from the negative value to the positive value, and the
deceleration adjustment by the power running operation by the motor
4 starts. However, the vehicle may be stopped using the friction
brake 12 without starting the power running operation by the motor
4 and the stop state may be maintained. Even if the
friction-braking-amount command value Tb* becomes 0 at the point
where the third torque target value Tm3* switches from the negative
value to the positive value, and the deceleration adjustment by the
power running operation by the motor 4 starts, the friction brake
12 may be actuated at the vehicle speed being approximately 0 to
maintain the stop state. To actuate the friction brake 12 to
maintain the stop state, the friction-braking-amount command value
Tb* is set to a value decided on the basis of the disturbance
torque estimated value Td at the vehicle speed of approximately
0.
[0086] Subsequently, the following describes the control result
when the vehicle stops on the flat road with reference to FIG. 8B.
The disturbance torque estimated value Td on the flat road is set
to 0.
[0087] At the time t1 at which the vehicle is prior to just before
the stop, the first torque target value Tm1* calculated in Step
S202 in FIG. 2 is set to the third torque target value Tm3*. The
vehicle decelerates according to the friction-braking-amount
command value Tb* decided on the basis of the first torque target
value Tm1* (=third torque target value Tm3*).
[0088] At the time t2, when the second torque target value Tm2* is
larger than the first torque target value Tm1* and it is determined
that the vehicle is just before the stop, the third torque target
value Tm3* switches from the first torque target value Tm1* to the
second torque target value Tm2*. Accordingly, the
friction-braking-amount command value Tb* also switches from the
value decided on the basis of the first torque target value Tm1* to
the value decided on the basis of the second torque target value
Tm2*.
[0089] From the times t2 to t5, the second torque target value Tm2*
asymptotically converges to 0 (disturbance torque estimated value
Td) according to the reduction in the motor rotation speed
.omega.m. This also causes the third torque target value Tm3* to
asymptotically converge to 0. Therefore, the
friction-braking-amount command value Tb* also asymptotically
converges to 0 (disturbance torque estimated value Td) and the
motor rotation speed .omega.m also asymptotically converges to 0.
This achieves the smooth vehicle stop without the acceleration
vibration in the longitudinal direction. At the time t5 and after
the time t5, the vehicle stop state is maintained.
[0090] Finally, the following describes the control result when the
vehicle stops on the downhill road with reference to FIG. 8C. At
the time t1 at which the vehicle is prior to just before the stop,
the first torque target value Tm1* calculated in Step S202 in FIG.
2 is set to the third torque target value Tm3*. The vehicle
decelerates according to the friction-braking-amount command value
Tb* decided on the basis of the first torque target value Tm1*
(=third torque target value Tm3*).
[0091] At the time t2, when the second torque target value Tm2* is
larger than the first torque target value Tm1* and it is determined
that the vehicle is just before the stop, the third torque target
value Tm3* switches from the first torque target value Tm1* to the
second torque target value Tm2*. Accordingly, the
friction-braking-amount command value Tb* also switches from the
value decided on the basis of the first torque target value Tm1* to
the value decided on the basis of the second torque target value
Tm2*. At the time t2 or after the time t2, the second torque target
value Tm2* (=third torque target value Tm3*) converges to the
disturbance torque estimated value Td according to the reduction in
the motor rotation speed .omega.m.
[0092] At the time t5, the friction-braking-amount command value
Tb* converges to the value decided on the basis of the disturbance
torque estimated value Td and the motor rotation speed .omega.m
asymptotically converges to 0. This achieves the smooth vehicle
stop without the acceleration vibration in the longitudinal
direction. Since the friction-braking-amount command value Tb*
converges to the value decided on the basis of the disturbance
torque estimated value Td, the vehicle stop state is maintained by
the friction brake 12 on the downhill road as well after the time
t5.
[0093] The above-described control device for vehicle of the one
embodiment is the device that generates the friction braking force
to decelerate the vehicle. The control device for vehicle estimates
the disturbance torque acting on the vehicle. When the accelerator
operation amount is equal to or less than the predetermined value
and the vehicle is just before the stop of the vehicle, the control
device for vehicle causes the friction braking amount to converge
to the friction braking amount to the value decided on the basis of
the disturbance torque estimated value Td in conjunction with the
reduction in the motor rotation speed (speed parameter)
proportionate to the traveling speed of the vehicle. This achieves
the smooth deceleration without the acceleration vibration in the
longitudinal direction just before the stop of the vehicle
regardless of the flat road, the uphill road, and the downhill road
and additionally ensures maintaining the vehicle stop state. The
deceleration or the stop of the vehicle is achieved by the
actuation of the friction brake 12 through the command from the
motor controller 2 and the brake controller 11. This eliminates the
need for switchingly depressing the accelerator pedal and the brake
pedal by the driver, ensuring reducing the load applied to the
driver.
[0094] It should be noted that, the accelerator operation amount is
equal to or less than the predetermined value intends the
accelerator operation amount when the vehicle sufficiently travels
at a low speed, for example, a speed of 15 km/h or less. It should
be noted that, needless to say, the exemplary vehicle speed is one
example.
[0095] Currently, studies on a vehicle that can control the
acceleration and deceleration and the stop of the vehicle only the
accelerator pedal operation have advanced. In this vehicle,
reducing or zeroing a depression amount of the accelerator pedal
depressed by the driver allows the vehicle to stop by the
regenerative braking force from the motor. However, for example, in
the case where an SOC of a battery is high such as the case where
the battery is fully charged, this vehicle restricts the motor
regeneration amount. In such case, the vehicle cannot be
decelerated and stopped using the regenerative braking force from
the motor. However, the control device for vehicle according to the
embodiment can actuate the friction brake 12 by the command from
the controller to decelerate and stop the vehicle. Accordingly,
even with the battery 1 in the high SOC state, the vehicle can be
smoothly decelerated and stopped.
[0096] The control device for vehicle of the one embodiment
multiplies the motor rotation speed .omega.m by the predetermined
gain Kvref to calculate the motor rotation speed F/ B torque T. The
control device for vehicle decides the friction braking amount on
the basis of the calculated motor rotation speed F/B torque
T.omega.) and the disturbance torque estimated value Td. The motor
rotation speed F/B torque T.omega., which is calculated by the
multiplication of the motor rotation speed .omega.m by the
predetermined gain Kvref, works as a viscosity (damper) element
with respect to dynamic characteristics from the motor torque until
the motor rotation speed. Accordingly, the motor rotation speed
.omega.m asymptotically and smoothly converges to 0 just before the
stop of the vehicle. This achieves the smooth vehicle stop without
a shock in the longitudinal acceleration.
[0097] The control device for vehicle of the one embodiment
estimates the disturbance torque on the basis of the model Gp(s)
for the transfer characteristic of the motor rotation speed with
respect to the torque input to the vehicle and the friction braking
amount. The estimation of the disturbance torque on the basis of
the model Gp(s) can accurately estimate the disturbance torque or
estimates the disturbance torque taking the friction braking amount
into consideration, thereby ensuring the estimation of the
disturbance torque excluding the friction braking amount acting on
the vehicle.
[0098] As the friction braking amount used by the disturbance
torque estimator 502 to estimate the disturbance torque, the
friction braking amount calculated on the basis of the brake fluid
pressure detected by the fluid pressure sensor 10 can be used. This
allows accurately estimating the disturbance torque excluding the
friction braking amount taking the actual friction braking amount
acting on the vehicle into consideration.
[0099] By the use of the friction-braking-amount command value as
the friction braking amount used by the disturbance torque
estimator 502 to estimate the disturbance torque, an influence from
a detection delay time of the sensor is not given compared with the
case of the detection of the friction braking amount using the
sensor such as the fluid pressure sensor 10. This allows accurately
estimating the disturbance torque excluding the friction braking
amount.
[0100] With the control device for vehicle of the one embodiment,
the disturbance torque estimator 502 calculates the disturbance
torque estimated value Td on the basis of the model Gp(s) for the
transfer characteristic of the motor rotation speed with respect to
the torque input to the vehicle, the model Gb(s) for the transfer
characteristic of the motor rotation speed with respect to the
friction braking amount input to the vehicle, and the friction
braking amount. Taking the response from the
friction-braking-amount command value until the generation of the
brake fluid pressure and the response from the generation of the
brake fluid pressure until the braking force acts on the wheel via
the brake pad into consideration ensures reducing the difference
between the vehicle model and the actual response of the
vehicle.
[0101] The control device for vehicle of the one embodiment
calculates the first torque target value Tm1* on the basis of
vehicle information and calculates the second torque target value
Tm2* converged to the disturbance torque estimated value in
conjunction with the reduction in the motor rotation speed
.omega.m. The comparison of the magnitudes of the first torque
target value with the second torque target value determines whether
the vehicle is just before the stop. When the control device for
vehicle determines that the vehicle is not just before the stop,
the control device for vehicle decides the friction braking amount
on the basis of the first torque target value Tm1*. When the
control device for vehicle determines that the vehicle is just
before the stop, the control device for vehicle decides the
friction braking amount on the basis of the second torque target
value Tm2*. This allows switching without discontinuity when the
friction braking amount is switched from the value on the basis of
the first torque target value Tm1* to the value on the basis of the
second torque target value Tm2* just before the stop of the
vehicle. Since the friction braking amount is decided on the basis
of the larger value among the first torque target value Tm1* and
the second torque target value Tm2*, torque discontinuity does not
occur in any gradient, thereby achieving the smooth
deceleration.
[0102] Furthermore, when the accelerator operation amount is equal
to or less than the predetermined value and the vehicle is just
before the stop on the uphill road, the motor torque command value
Tm* is converged to the disturbance torque estimated value Td in
conjunction with the reduction in the motor rotation speed
.omega.m. Therefore, the smooth vehicle stop from the deceleration
is achieved even on uphill roads, thereby ensuring maintaining the
vehicle stop state.
[0103] The present invention is not limited to the above-described
one embodiment. For example, the above-described embodiment
describes the example of the application of the control device for
vehicle to the electric vehicle. However, since the control device
for vehicle of the present invention is applicable to the vehicle
that can electrically adjust the friction braking amount, the
application target is not limited to the electric motor vehicle
with the motor as the driving source.
[0104] The above-described explanation describes that, when the
accelerator operation amount is equal to or less than the
predetermined value and the vehicle is just before the stop, the
friction braking amount converges to the disturbance torque
estimated value Td in conjunction with the reduction in the motor
rotation speed .omega.m. However, since the speed parameters such
as the wheel speed, the vehicle body speed, and the rotation speed
of the drive shaft are proportional relationship with the rotation
speed of the electric motor 4, the friction braking amount may be
converged to the disturbance torque estimated value Td in
conjunction with the reduction in speed parameter, which is
proportionate to the rotation speed of the motor 4.
* * * * *